Heres a short tutorial for doin this urself
1 download war3modeleditor in the tools section
2 open it, then go to windows/mpq browser
3 open the mpq its in (war3.mpq in this case)
4 open ur mdl
5 save ur model in the same folder as your texture
5 go to windows/texture manager
6 import your texture
7 go to windows/material manager
8 double click the first material layer, then when it opens, click on the material, (usually bottom one, since bottom, is the outermost layer, and teamcolored is above)
9 if this layer has the path of the old texture, units/undead/abom, or w/e it is, in this case. click the drop down arrow, and choose your new texture
go back to starting screen and go to file/save as, save it with a new name...
there ya go, for the new path just remove war3mapimported/ in world editor
If ya need help send me a PM, (or if for some reason you cant do this)